Skip stitch mechanism for household sewing machines

ABSTRACT

A needle bar reciprocation interrupting mechanism is disclosed for sewing machines by which the formation of stitches may be intentionally skipped so that extremely long stitches as for basting may be formed, or by which isolated stitch groups may be sewn. In the mechanism disclosed the stitches will be skipped each time the zigzag mechanism jogs the needle bar beyond a range of positions in which it can cooperate with the stitch-forming mechanism to form a stitch. In this manner the complete range of zigzag stitch capabilities of the sewing machine will remain available and the skip stitch mechanism does not require any more than setting of the conventional zigzag control means to render it selectively effective. Also disclosed is a safety cam means by which the needle bar when jogged to an abnormal position will automatically be deflected back into the range of positions capable of forming a stitch in the event that the needle bar interrupting means should accidentally malfunction.

United States Patent 72] Inventor Edward J. Tullman Union, NJ. [2]] App]. No. 848,175 [22] Filed Aug. 7, 1969 [45] Patented Feb. 2, 1971 [73] Assignee The Singer Company New York, N.Y. a corporation of New Jersey [54] SKIP STITCH MECHANISM FOR HOUSEHOLD 3,433,190 3/1969 Sagi Primary Examiner-Richard J. Scanlan, Jr. Attorneys-Marshall J. Breen, Chester A. Williams, Jr. and

Robert E. Smith ABSTRACT: A needle bar reciprocation interrupting mechanism is disclosed for sewing machines by which the formation of stitches may be intentionally skipped so that extremely long stitches as for basting may be formed, or by which isolated stitch groups may be sewn. In the mechanism disclosed the stitches will be skipped each time the zigzag mechanism jogs the needle bar beyond a range of positions in which it can cooperate with the stitch-forming mechanism to form a stitch. In this manner the complete range of zigzag stitch capabilities of the sewing machine will remain available and the skip stitch mechanism does not require any more than setting of the conventional zigzag control means to render it selectively effective. Also disclosed is a safety cam means by which the needle bar when jogged to an abnormal position will automatically be deflected back into the range of positions capable of forming a stitch in the event that the needle bar interrupting means should accidentally malfunction.

P'ATENIEH FEB 2191:

SHEET 1 OF 2 INVENTOR Edward J. Tullmon ATTORNEY PATENIED FEB 2197:

SHEET 2 BF 2 ATTORN SKIP STITCH MECHANISM FOR HOUSEHOLD SEWIN MACHINES BACKGROUND OF THE INVENTION This invention relates to skip stitch mechanisms for sewing machines, and more particularly, to a skip stitch mechanism which may be applied readily to any existing zigzag-sewing machine with a minimum of alteration and without detracting from the range of sewing capabilities or from the permissible width of zigzag stitch capability of the sewing machine to which this invention is applied. The U.S. Pat. No. 3,433,190, Mar. 18, 1969 to Zigmund Sagi discloses a skip stitch mechanism for a zigzag-sewing machine in which, as in the present invention, the operation of the needle jogging mechanism of the sewing machine is also utilized selectively to effect skip stitching. In this patented construction, however, the skip stitch mechanism. when effective, decreases appreciably the width of the zigzag stitching which the sewing machine is capable of producing. As a consequence, in order for the sewing machine to possess the full zigzag stitching capability, a control device is required, in addition to the conventional zigzag controls, by which the skip stitch mechanism may be selectively rendered effective and ineffective. The present invention is an improvement of the construction disclosed in the above-mentioned U.S. Pat. No. 3,433,190 in that any control means over and above the conventional zigzag controls for selectively rendering the skip stitch mechanism effective and ineffective may be dispensed without depriving the sewing machine of the full stitching capacity which it would have in the complete absence of the skip stitch mechanism.

The U.S. Pat. No. 3,433,189, Mar. 18, 1969 to W. Weisz discloses another form of skip stitch mechanism for sewing machines in which the interruption of the needle bar reciprocation is effected by a mechanism which is separate and distinct from the zigzag mechanism of the sewing machine. While the skip stitch mechanism of the U.S. Pat. No. 3,433,189 does not detract from the sewing capabilities of the sewing machine, this patented mechanism does require a far more complicated and costly needle bar interrupting mechanism than does the present invention which utilizes to a large extent the zigzag mechanism of the sewing machine for the double purpose of zigzag stitching as well as interruption of needle bar reciprocation for skip stitching.

SUMMARY OF THE INVENTION The aforementioned objects and advantages of this invention are attained by the provision in a zigzag-sewing machine of a mechanism for imparting lateral jogging movement to the needle bar beyond the range in which the needle bar can cooperate with the other stitch forming instrumentalities of the sewing machine to form stitches. A needle bar reciprocation interrupting means is provided which is effective to stop needle penetration only during lateral movement of the needle bar beyond the range of sewing positions of the zigzag needle.

A further feature of this invention is a safety cam disposed in the path of reciprocation of means on the needle bar while the needle bar is jogged beyond the predetennined sewing range of positions, which safety cam serves to deflect the needle bar back into the predetermined sewing range of positions in the event that the needle bar reciprocation interrupting means should inadvertently fail to be-effective.

DESCRIPTION or THEDRAWINGS With the above and additional objects and advantages in view, as will hereinafter appear, this invention comprises the devices, combinations, and arrangements of parts hereinafter described and illustrated in the accompanying drawing of a preferred embodiment in which:

FIG. 1 represents a perspective view of the skip stitch mechanism of this invention including only portions of the salient mechanisms of a sewing machine and illustrating the needle bar held in the elevated skip stitch position;

FIG. 2 is a front elcvational view of the sewing head portion of a sewing machine having the needle bar reciprocation interrupting means of this invention applied thereto and illustrating the manner in which the safety cam means deflects the needle bar in the event that the needle bar is inadvertently not detained in elevated position;

FIG. 3 is a front elevational view of a portion of the needle bar reciprocation interrupting means of FIG. 1 showing the latch means on the needle bar disengaged from the needle barreciprocating drive means and interengaged with the keeper for retaining the needle bar substantially at the top of its stroke;

FIG. 4 is a left side elevational view of the spring biased latch lever of the needle bar reciprocation-interrupting means of FIG. 3;

FIG. 5 is a top plan view of a sewing machine with a portion of the top cover plate removed showing the skip stitch mechanism of this invention applied thereto but with the sewing machine parts in a position for sewing; and

FIG. 6 is a cross-sectional view taken substantially along line 6-6 of FIG. 5 showing the parts during skip stitching.

The present invention may be applied to any sewing machine equipped with a needle jogging mechanism for zigzag sewing. The accompanying drawings illustrate this invention applied to a sewing machine of the type illustrated in more detail in the copending U.S. application of March et al., Ser. No. 827,867, filed May 26, 1969, to which reference may be had.

As shown in the drawings, the sewing machine has a frame including a bracket arm 11 formed with a sewing head 12. Journaled in the bracket arm is a main drive shaft 13 which may be driven by an electric motor (not shown). A worm 14 on the main drive shaft meshes with a worm wheel 15 on a cam shaft 16 in the bracket arm to impart driving movement to a stack of pattern cams 17 on the cam shaft. Included on the top of the cam stack 17 is an exchangeable pattern cam 18 having a handle 19 which may be grasped by the operator in exchanging the pattern cam.

Journaled for swinging movement in the sewing head 12 on a vertical pin 21 is a needle bar gate 22 supporting a spherical bearing 23 for an endwise reciprocatory needle bar 24 carrying a needle 25 at its lower extremity. A second spherical bearing 26 for the needle bar is constrained in the sewing head 12 so that in addition to endwise reciprocation the needle bar can be jogged laterally as for the formation of zigzag stitches. For imparting endwise reciprocation to the needle bar, the main drive shaft 13 carries a counterbalanced crank 27 connected to a needle bar drive link 28 which embraces a stud 29 which is sustained on the needle bar by a block 30 provided with check pieces 31. The block 30 is not secured directly to the needle bar, but instead is freely slidable lengthwise thereon. Above the block 30 a collar 32 is securely fastened to the needle bar by a set screw 33. Pivoted to the collar 32 by a shoulder screw 34 is a latch lever 35 having an upstanding finger 36 and a depending arm 37. The depending arm 37 is formed with a lateral latch finger 38 shown in FIG. 1 adapted to engage beneath a latch notch 39 formed in the cheek piece 31 of the block 30 so as to secure the block 30 and the collar 32 together and thus complete an endwise reciprocatory needle bar driving connection between the needle bar 24 and the drive link 28. A coil spring 40 shown in FIG. 4 engages the latch lever 35 and the collar 32 and biases the latch finger 38 toward operative engagement with the latch notch 39 in the cheek piece 31.

A sheet metal angle bracket 41 is constrained on the collar 32 by the shoulder screw 34 and by an inturned limb 42 which extends alongside the collar 32. The angle bracket 41 is formed with an inturned abutment stop 43 disposed in the path of motion of the latch lever 35. It is the function of the abutment stop 43 to prevent the latch finger 38 from being shifted into a position excessively near the needle bar. The abutment stop 43 will prevent the latch finger 38 from being turned beyond a point in which the inclined upper edge 44 of the cheek piece 31 can contact and urge the latch finger 38 outwardly and about the cheek piece and into cooperation with the latch notch 39.

For stabilizing the needle bar 24 when the block 30 is engaged with the collar 32, the collar 32 is formed with a depending projection 45 which fits snuggly between the cheek pieces 31 on the block 30.

Lateral jogging motion is imparted to the needle bar as for zigzag sewing by means of a zigzag drive link 50 which is pivotally connected to the needle bar gate 22 and has an integrating plate 51 pivoted thereon at 52 remote from the needle bar gate and adjacent to the cam stack. A spring 53 anchored in the bracket arm urges the drive link 50 and the integrating plate 51 toward the cam stack. Two pattern cam followers 54 and 55 are interposed between the integrating plate 51 and the cam stack, each pattern cam follower being slidably pivoted on a respective stud 56, 57 in the bracket arm. For each cam follower a cam selecting mechanism is provided. FIG. illustrates at 60 a cam selecting mechanism for ,the front cam follower 54. The cam selector mechanism 60 comprises a lever system slidably joumaled on a rod 61 arranged transversely of the bracket arm and having an operator influenced knob 62 secured on an exposed arm 63 of the lever system. Axial motion of the lever system by depression of ,the knob 62 serves by way of axial shift of a lever arm 64 to engage a tail portion 65 of the front cam follower 54 to shift the pattern cam follower 54 out of engagement with the cam stack.

Turning of the lever system about the rod 61 serves by way of a link 66 to shift the follower along its support stud 56 into tracking relation with a selected pattern cam on the cam shaft 16.

A similar cam-selecting mechanism is provided for the rear pattern cam follower so that the followers may be placed in tracking relation with any desired pattern cam in the stack and at least the front follower 54 may be placed in tracking relation with an exchangeable cam 18 atop the cam stack.

The stack of cams 17 and the exchangeable cam 18 constitute selectable response producing records each having peripheral cam tracks of which the radius can vary within predetermined limits and when tracked by one or both of the followers 54, 55 serve to jog the needle bar for the production of zigzag stitches.

Pivoted on the cam shaft 16 beneath the stack of cams 17 is a bight control lever 70 having an operator influenced handle 71 thereon. Pivotally connected to the bight control lever 70 as by spherically headed stud 72 is the drive link 50 of the needle jogging mechanism. By this connection with the bight control lever, the integrating plate 51 may be shifted laterally relatively to the two cam followers 54 and 55. When the bight adjusting lever handle 71 is positioned in the setting corresponding to maximum bight or width of zigzag stitching as illustrated in FIG. 5, the center line of the pivotal connection 52 of the integrating plate is placed directly opposite to the front follower 54 which cancels out all influence of the rear cam follower 55 on the integrating plate. It is in this position of adjustment of sewing machine controls that the skip stitch mechanism of this invention can be operative.

Referring to FIGS. 1, 2 and 3 in which the needle bar mechanism is shown in detail, 80 represents a bracket which is supported within the sewing head 12, as is conventional in this type of sewing machine for supporting adjusting mechanism, such as a dial (not shown) or the like for adjusting the downward spring pressure which is applied to a presser bar 82, slidable in the sewing head 12 and carrying at its lower extremity a conventional presser foot 83. The bracket 80 may be formed with a sloping abutment surface 84 which is positioned for engagement with the upstanding finger 36 of the latch lever 35 at the upstroke of the needle bar reciprocation whenever the needle bar is jogged laterally beyond that lateral position which exceeds its capability to form a stitch. The abutment surface 84 may also be formed on a separate plate secured to the bracket 80, or secured directly to the sewing machine frame. With reference to FIG. 1, it will be noted that the presser foot 83 is formed with a laterally elongated opening 86 for needle penetration. This presser foot needle aperture 86 conventionally corresponds in width with a needle aperture (not shown) formed in a throat plate 87 on which work is supported on the sewing machine. The needle apertures are formed sufi'iciently wide to accommodate the widest bight for lateral jogging movement which the needle is capable of making commensurate with the ability of the sewing instrumentalities to make a stitch. If the needle bar were to be jogged a greater distance laterally than is provided by the presser foot aperture 86, the needle would, of course, strike the presser foot and damage to the parts would result. When the term lateral jogging beyond a range in which stitches are capable of being formed" is used in this specification, however, it will include not only limitations imposed by the width dimension of the needle aperture in the presser foot or throat plate, but will include also any limitations in the capability of the needle and loop taken to cooperate in the formation of stitches. The abutment surface 84 is so positioned on the bracket as to engage the upstanding finger 36 and shift the latch lever 35 so as to disengage the latch finger 38 from the latch notch 39 whenever, for any reason, the needle bar is jogged beyond that point in which it is capable of forming a stitch. Since the abutment surface 84 is disposed on the lefthand side of the collar 31 as viewed in FIGS. 1, 2 and 3, it will be apparent that disengagement of the latch lever 35 will be effected only when the needle bar is jogged in a direction to shift the needle to the right as viewed in FIGS. 1 and 2. It will be understood, however, that the abutment surface 84 may be placed at the opposite side of the needle bar and the latch lever 35 may be reversed so as to disengage the needle bar when it is jogged beyond a stitching range in the opposite direction. For influencing separation of the drive for endwise reciprocation of the needle bar to cause skipped stitches with this invention a special response producing record preferably in the form of a pattern cam may be inserted atop the cam stack 17 in place of a pattern cam which is capable only of influencing patterns of zigzag stitches. Such a pattern cam for skip stitching is illustrated at 90 in FIGS. 1, 5 and 6, and is characterized by peripheral cam surfaces 91 which are formed at a smaller radius than the smallest radius portions of any of the zigzag pattern cams in the stack 17. The skip stitch cam 90 is also formed with peripheral portions 92 which are disposed at a radius as large as than of the cam track portions of the zigzag pattern cams in the zigzag pattern cam stack 17. When the bight control handle 71 is shifted to the position of maximum bight as illustrated in FIG. 5 and a skip stitch cam 90 is positioned on the cam stack with the front follower 54 selectedto track the skip stitch cam 90, those portions 91 of the skip stitch cam which are of smaller radial dimension than the smallest radius of any zigzag cam will shift the needle bar beyond the range of positions in which it is capable of forming stitches, and on the succeeding upstrike of the needle the upstanding finger 36 of the latch lever 35 will strike the abutment surface 84 and separate the connection between the drive link 28 and the needle bar 24.

A resilient stop lug is secured by a screw 101 to the sewing head 12 in the path of reciprocation of the needle bar so as to prevent the needle bar from flying upwardly in an uncontrolled manner when the drive connection thereto is disengaged during high-speed operation of the machine.

Secured as by a fastening screw 111 to the presser regulating bracket 80 is a retaining bracket 110. An inturned shoulder portion 112 of the retaining bracket is arranged in the path of the latch finger 38 of the latch lever 35 when the latch lever is forced out of operative engagement with the cheeks 31 of the block 30 as illustrated in FIG. 1. The shoulder portion 112, thus by engaging the latch lever 35,

maintains the needle bar in elevated position while the block 30 slides downwardly relatively to the needle bar. Depending from the shoulder portion 112 of the retaining bracket and in the path of movement of the latch finger 38 of the latch lever lever 35 is an inclined cam arm portion 113 of the retaining bracket 110 which functions as is illustrated in FIG. 2 to urge the latch lever 35 and the needle bar 24 to the right as viewed in FIG. 2 in the event that the retaining shoulder portion 112 of the bracket 110 should accidentally fail to retain the needle bar in an elevated position during a skip stitch. Preferably, tire inclined cam arm 113 of the retaining bracket should be adjusted very accurately so as to urge the needle bar sufficiently to prevent the needle from striking the edge of the presser foot or from striking the work support of the sewing machine and to this end an abutment stud 114 may be provided threaded into the inclined cam arm portion 113 of the retaining bracket 110 and adapted to engage the sewing head 12. The abutment stud is provided with a nut 115 which may be adjusted so as to position the retaining bracket very accurately relatively to the sewing head.

It will be appreciated that the abutment surface 84 and the retaining bracket 110 may be supported other than by the presser foot pressure regulator bracket 80 and, for instance, may be attached directly to the sewing head portion 12 of the sewing machine frame. By being carried on the bracket 80, however, the abutment surface 84 and retaining bracket 110 may be provided as a subassembly thereto facilitating manufacture of the sewing machine. 5

In FIG. 1 is illustrated a stitched material 120 to which long stitches are being applied using the skip stitch cam 90 illustrated in FIGS. 1, 5 and 6. This skip stitch cam 90 is formed with two diametrically spaced large diameter cam track portions 92, each portion occupying only one arm shaft revolution of the sewing machine in engagement with cam follower 54. All other cam track portions 91 of the skip stitch cam 90 are of small diameter and influence the skip stitch mode so that with a conventional drive ratio of 24 stitches for each rotation of the cam shaft 16, the cam 90 will cause the needle bar reciprocating mechanism to partake of 11 cycles of motion with the needle bar disengaged for each cycle of motion with the needle bar operatively connected and exceedingly long stitches as illustrated in FIG. 1 will result. If the stitch length of the conventional sewing machine work feed is set, for instance, at approximately Va of an inch per stitch, the stitches illustrated in FIG. 1 will be spaced by approximately 1 of an inch and such stitches will be useful as basting stitches. Other configurations of skip stick earns 90 may be used, for instance, to produce conventional zigzag stitches during one portion of a cam shaft rotation and skip stitches during another portion thereof so as to provide for spaced groups of zigzag stitches.

Furthermore, the invention is not limited to the use of a pattern cam for producing jogging motion of the needle beyond the range in which stitching can be accomplished and during which the skipped stitches will be provided. Any desired control for effecting such abnormal lateral jogging movement may be used as, for instance, a manual instrumentality whereby skip stitches may be caused to be formed at will simply by effecting an abnormal jogged position of the needle bar.

1 claim:

l. A skip stitch mechanism in a sewing machine having a frame, actuating mechanism carried in said frame, a needle bar carried by said frame for endwise reciprocation and for lateral jogging movement for the formation of zigzag stitches, means on said sewing machine establishing a predetermined range of laterally jogged positions of said needle bar in which it is possible for stitches to be formed, means driven by said actuating mechanism for imparting endwise reciprocation to said needle bar, mechanism driven by said actuating mechanism for imparting lateral jogging movement to said needle carrying bar within said predetermined range of laterally jogged positions, means for influencing the lateral jogging movement of said needle bar beyond said predetermined range of laterally jogged positions, and interrupting means for said needle bar reciprocating means effective only during lateral jogging movement of said needle bar beyond said predetermined ran e.

2. A skip stitch mec anism as set forth in claim 1 in which said mechanism for imparting lateral jogging movement to said needle bar within said predetermined range in which it is possible for stitches to be formed is adapted to be influenced by a selectable response producing record, and in which said means for influencing lateral jogging movement of said needle bar beyond said predetermined range includes a different response producing record substitutable in said mechanism for imparting lateral jogging movement to said needle in place of a response producing record for said predetermined range of laterally jogged positions.

3. A skip stitch mechanism as set forth in claim 2 in which said response producing record for imparting lateral jogging movement to said needle bar within said predetermined range comprises a rotary pattern cam having a peripheral cam track of which the radius varies within predetermined limits, and in which said means for influencing lateral jogging movement of said needle bar beyond said predetermined range includes a rotary pattern cam having a peripheral cam track with portions formed at a radius smaller than said predetermined limits of a pattern cam for stitching.

4. A skip stitch mechanism as set forth in claim 1 in which said needle bar is driven in only one direction by said mechanism for imparting lateral jogging movement to said needle bar and in which means biases said needle bar in the opposite direction, and in which said interrupting means includes interengaging latch means on said needle carrying bar and on said means for imparting endwise reciprocation to said needle carrying bar, and abutment means carried by said sewing machine frame and located for contact with said latch means to effect unlatching thereof only during lateral jogging movement of said needle bar beyond said predetermined range in said opposite direction, and in which safety cam means is carried by said sewing machine frame and disposed in the path of reciprocation of means on said needle bar when said needle bar is jogged in said opposite direction beyond said predetermined range of laterally jogged positions so as to deflect said needle bar in opposition to the bias and into said predetermined range.

5. A skip stitch mechanism as set forth in claim 4 in which a keeper element adjoins said safety cam means and cooperates with said latch means on said needle bar for retaining said interrupted needle bar substantially at the top of said needle bar reciprocation. 

1. A skip stitch mechanism in a sewing machine having a frame, actuating mechanism carried in said frame, a needle bar carried by said frame for endwise reciprocation and for lateral jogging movement for the formation of zigzag stitches, means on said sewing machine establishing a predetermined range of laterally jogged positions of said needle bar in which it is possible for stitches to be formed, means driven by said actuating mechanism for imparting endwise reciprocation to said needle bar, mechanism driven by said actuating mechanism for imparting lateral jogging movement to said needle carrying bar within said predetermined range of laterally jogged positions, means for influencing the lateral jogging movement of said needle bar beyond said predetermined range of laterally jogged positions, and interrupting means for said needle bar reciprocating means effective only during lateral jogging movement of said needle bar beyond said predetermined range.
 2. A skip stitch mechanism as set forth in claim 1 in which said mechanism for imparting lateral jogging movement to said needle bar within said predetermined range in which it is possible for stitches to be formed is adapted to be influenced by a selectable response producing record, and in which said means for influencing lateral jogging movement of said needle bar beyond said predetermined range includes a different response producing record substitutable in said mechanism for imparting lateral jogging movement to said needle in place of a response producing record for said predetermined range of laterally jogged positions.
 3. A skip stitch mechanism as set forth in claim 2 in which said response producing record for imparting lateral jogging movement to said needle bar within said predetermined range comprises a rotary pattern cam having a peripheral cam track of which the radius varies within predetermined limits, and in which said means for influencing lateral jogging movement of said needle bar beyond said predetermined range includes a rotary pattern cam having a peripheral cam track with portions formed at a radius smaller than said predetermined limits of a pattern cam for stitching.
 4. A skip stitch mechanism as set forth in claim 1 in which said needle bar is driven in only one direction by said mechanism for imparting lateral jogging movement to said needle bar and in which means biases said needle bar in the opposite direction, and in which said interrupting means includes interengaging latch means on said needle carrying bar and on said means For imparting endwise reciprocation to said needle carrying bar, and abutment means carried by said sewing machine frame and located for contact with said latch means to effect unlatching thereof only during lateral jogging movement of said needle bar beyond said predetermined range in said opposite direction, and in which safety cam means is carried by said sewing machine frame and disposed in the path of reciprocation of means on said needle bar when said needle bar is jogged in said opposite direction beyond said predetermined range of laterally jogged positions so as to deflect said needle bar in opposition to the bias and into said predetermined range.
 5. A skip stitch mechanism as set forth in claim 4 in which a keeper element adjoins said safety cam means and cooperates with said latch means on said needle bar for retaining said interrupted needle bar substantially at the top of said needle bar reciprocation. 